In this project the biology and immunology of acute leukemia are studied, with particular emphasis on investigation of acute lymphocytic leukemia. Leukemic lymphoblasts are being characterized on the basis of cell surface markers and specific antigens detectable by various monoclonal antibodies and heteroantisera. Such characterization permits comparison of leukemic and normal lymphoid cells in terms of cellular differentiation and malignant transformation. Biochemical studies, such as determination of the role of the purine pathway enzymes in lymphoid leukemia and lymphoma, permit insight into the relationship between malignant and normal lymphoid cells. Certain immunologic functions of leukemic lymphoblasts are studied such as their immunoregulatory capacity. Study of the role of the monocyte-macrophage system in the lymphoid malignancies is also in progress.